Apparatus for the manufacture of potassium

ABSTRACT

Production of metallic potassium. K2SO4 placed in a reactor is reduced by means of iron in the presence of CaO under reduced pressure and with supply of heat, and the resulting potassium, which distils over, is condensed.

[ Oct. 30, 1973 [56] References Cited UNITED STATES PATENTS HelmutSeifert, Hermulheim, near Cologne; Otto Bretsclmeider, Kirchzarten,Schwarzwald, all of Germany Knapsack, Germany Aug. 16, 1972 POTASSIUM[75] Inventors: Uwe Landt, Hurth, near Cologne;

Related U.S. Application Data [62] Division of Ser. No. 41,016, May 27,1970, Pat. No.

Foreign Application Priority Data June 25, 1969Germany...................

United States Patent [1 1 Landt et a1.

[ APPARATUS FOR THE MANUFACTURE OF [73] Assignee: KnapsackAkfiengesellschaft,

[22] Filed:

[21] Appl. No.: 280,982

[51] Int.

[58] Field of Search..................

APPARATUS FOR THE MANUFACTURE OF POTASSIUM This is a division ofapplication Ser. No. 41,016, filed May 27, 1970, now U.S. Pat. No.3,700,430.

The present invention relates to an apparatus for the production ofpotassium by thermochemical means.

Various processes for the thermochemical production of potassium havealready been described. The feed materials used therein primarilyinclude KF, KCl, K CO and KOH, and the reductants include C, CaC Si, Al,Mg or FeSi.

While the reduction of KF generally furnishes high yields of potassium,the fact remains that this is a commercially unattractive process inview of the relatively high price of potassium fluoride. Thesusceptibility to moisture of CaC which therefore is difficult tohandle, is a further disadvantage that handicaps the use of CaC in thereduction of KF, which has already been tried commercially. Stillfurther, it is impossible to operate in continuous fashion as thereaction produces compact solid material rather than a melt, and thissolid material is difficult to remove from the reactor.

More recently, it has repeatedly been suggested that KCl be used for theproduction of potassium. However, the relatively high vapor pressure ofKC] dictates the use of extensive and costly facilities to enable thepotassium, which distils over, to be isolated from KCl. While thereduction of K CO would appear to be a commercially attractive procedurewith respect to production costs, the fact remains that this process hasfailed to gain interest because of the formation of potassium carbonylduring the reaction and the inherent risks of explosion. The use of KOHas a feed material also fails to have beneficial effects as itshygroscopicity has been found to considerably handicap the course of thereaction.

The present invention now unexpectedly provides a apparatus for theproduction of pure potassium, which is free from the deficienciesreported above and more particularly combines the use of inexpensivefeed materials with continuous operation.

The present apparatus for the production of metallic potassium comprisesmore especially reducing K 50 in a reactor by means of iron in thepresence of CaO under reduced pressure and with the supply of heat,distilling off resulting potassium and condensing it.

The apparatus should conveniently be carried out while using between 1and 3 mols CaO, preferably 2 mols CaO, per mol K 80 and at least 5 gramatoms iron, again per mol K 80 The feed reactants should preferably bereduced at temperatures above 950C and under reduced pressure. The feedreactants are more preferably heated to temperatures of between 950 and1,300C, advantageously between l000 and 1,150C. under a pressure ofbetween 0.01 and 1.0 mm mercury, advantageously between 0.05 and 0.8 mmmercury.

These high temperatures make it desirable for the outer wall of thereactor to be maintained under pressure conditions substantially thesame as those which prevail inside the reactor.

Following termination of the reaction, the molten reaction products aredelivered to an evacuated container, and fresh feed material coming froma further evacuated container is fed to the reactor.

While it has long been known that potassium can be produced by reductionof IK SO by means of iron, the

fact remains that conventional processes produce material which isextremely viscous and almost solid at the reaction temperature.

It has now unexpectedly been found that the use of the feed reactants incombination with CaO in the proportions suggested hereinabove effectsthe formation of a melt that is flowable at the reaction temperature andtherefore can be tapped off continuously.

The reaction occurs substantially in conformity with the followingschematic equation:

The condensation of potassium in vapor form effects the formation ofvery pure metallic potassium. The reason for this is that contaminationof the feed reactants is obviated in the process of the presentinvention.

The iron may be used in powder form or in the form of waste sheet iron,turnings or scrap iron.

The present invention provides an apparatus for use in carrying out thepresent process. The chief requirements which such apparatus has to meetare fair unsusceptibility of the reactor to the attack of molten K 50,and resistance of the heating means firstly to the attack of molten K80. and secondly to the attack of potassium in vapor form or liquidform.

An apparatus which satisfies the requirements substantially comprises aclosed crucible receiving reaction material, at least one heat radiatorpositioned in the crucible at a place above the reaction material and anat least partially heatable conduit connecting the crucible to acondenser and a collector.

The crucible is further fitted with a junction line connecting itsinterior to a vacuum pump.

In accordance with a preferred feature of the present invention, thecrucible is most advantageously a chrome-nickel-molybdenum steelcrucible.

The heat radiator may comprise one or more electrically heated graphiteelements, of which the power leads are arranged so as to project intothe crucible and enveloped therein by a jacket comprising a graphitebase portion and steel head portion.

The crucible is preferably arranged to be additionally surrounded by afurnace fitted with a heater and a junction line connecting it to avacuum pump.

The crucible is further provided with a cover which receives the heatradiator and the heatable conduit and which is arranged to be connectedin airtight fashion, preferably by means of a water-cooled flange, tothe furnace.

The crucible base portion may be connected to a container for theremoval of slag under vacuum, and the crucible head portion may beconnected to a reservoir, preferably a vacuum lock, for the supply ofreaction material under vacuum to the crucible, the said container beingconnected to the crucible by means of a heatable conduit.

The apparatus will now be described in greater detail with reference tothe exemplary embodiment shown in the accompanying drawing.

As can be seen, furnace l and its cover 2 are connected together inairtight fashion by means of watercooled flange 3. The two structuralparts are lined with a high temperature-resistant tamping mass, forexample A1 0 The reactor is a Cr-Ni-Mo-steel crucible 4 (V4A steelstainless steel) which is arranged to be surrounded by an electricresistance heating 5 comprising a plurality of conventional heatingrods. The heating system enables thematerial which is to undergoreaction to be heated up to a temperature of substantially 800C. C. Bymeans of one or more graphite radiators ll, which are arranged toproject into crucible 4, it is possible to very rapidly heat thereaction material to the necessary reaction temperature of more than950C; in addition thereto, it is possible to rapidly correct thetemperature. Heating element ll may comprise, for example, a graphitetube 6 provided with helical slits, or a plurality of graphite rods.

Electric power is supplied through lead 14 surrounded by protectingjacket 12, of which the lower third is of graphite and the upper twothirds are of steel, because of the aggressiveness of condensedpotassium towards graphite.

The reactor is evacuated via line 7; potassium in vapor form issuction-drawn through line 8 heated to a temperature of between 350 and400C by means of a heating coil. Near the end of pipe 8, which issurrounded by air cooler 9, the potassium in vapor form is condensed anddelivered in liquid phase to container 13. Junction line 10 is used toproduce in the space left between the crucible and the tamping mass avacuum substantially of the same order as that established in thereactor itself. This is done to have a crucible of satisfactorystrength.

For continuous operation, the apparatus may be connected to valvedcontainers and 16, which firstly enable the reactor to be fed with feedmaterial and secondly enable liquid slag to be tapped off through heatedconduit 17, under vacuum or inert gas.

The following Examples illustrate the apparatus of the presentinvention.

EXAMPLE 1:

610 grams K 80 390 grams CaO and 980 grams iron in powder form weremixed together and the resulting mixture was introduced into a reactioncrucible of V4A-steel (stainless steel). The furnace was closed,evacuated and the crucible with the feed material therein was heated toa temperature of 800C, by means of heating rods. The discharge pipe,through which potassium in vapor form was removed, was simultaneouslyheated to a temperature of 350C. By means of the graphite heatingelements, it was possible very rapidly to increase the temperatureprevailing in the crucible to substantially 1,000C. The potassiumcommenced to distil off at a temperature of 1,020C and under a pressureof 0.25 mm mercury, measured in the crucible bottom portion; from l,060Cupward until termination of the experiment, all the material present inthe crucible was in the form of a melt. The potassium ceased to distilover after 3 hours at a final temperature of l,l30C and under a pressureof 0.06 mm mercury. The yield was 86 percent, based on the quantity of K80 used.

EXAMPLE 2:

610 grams K 80 and 390 grams CaO were mixed and introduced together with980 grams waste sheet iron into a reactor the same as that used inExample I. The reactor was evacuated and heated in the manner describedin the preceding Example. The reaction material commenced to partiallypass into the liquid state at l,l00C and 0.6 mm mercury, and potassiumbegan to distil over at l,l20C and 0.4 mm mercury. The reaction wascomplete after about 2 A hours at l,l4()C and under a pressure of 0.1 mmmercury. The yield was 84 percent.

We claim:

1. Apparatus for making metallic potassium from a reaction mixture,comprising a furnace and a crucible; the crucible being suspended in thefurnace so as to be spaced from the inside wall of the furnace andprovide an interspace bounded by the inside wall of the furnace and theoutside wall of the crucible; an overhead cover effecting gas-tightsealing between the furnace and the crucible; a conduit opening fromoutside the furnace into the interspace between the inside wall of thefurnace and the outside wall of the crucible and connecting theinterspace to a vacuum pump; at least one radi ator projecting throughthe cover into the interior of the crucible to provide heat forvaporizing metallic potassium from the reaction mixture; a furtherconduit projecting outwardly from the interior of the crucible andconnecting the crucible to a condenser and a further vacuum pump forrecovering and condensing the vaporized mixture, and heating means beingdisposed in heat exchange relationship over at least a portion of thelength of the further conduit.

2. The apparatus as claimed in claim 1, wherein the crucible is achrome-nickel-molybdenum steel crucible.

3. The apparatus as claimed in claim 1, wherein the heat radiatorcomprises one or more electrically heated graphite elements, whose powerleads are arranged so as to project into the crucible and envelopedtherein by a jacket.

4. The apparatus as claimed in claim 3, wherein the jacket has agraphite base portion and a steel head portion.

5. The apparatus as claimed in claim 1, wherein the radiator comprises ahelically slitted graphite tube.

6. The apparatus as claimed in claim 1 wherein a heating system isdisposed within the interspace.

7. The apparatus as claimed in claim 1 wherein the cover, the crucibleand the furnace are connected together by means of a water-cooledflange.

8. The apparatus as claimed in claim 1, wherein the crucible baseportion is connected to a container permitting the removal of slag undervacuum, and the crucible head portion is connected to a valved reservoirpermitting the supply of reaction material to the crucible, undervacuum.

9. The apparatus as claimed in claim 8, wherein the container is fittedwith a heatable conduit connecting it to the crucible.

2. The apparatus as claimed in claim 1, wherein the crucible is achrome-nickel-molybdenum steel crucible.
 3. The apparatus as claimed inclaim 1, wherein the heat radiator comprises one or more electricallyheated graphite elements, whose power leads are arranged so as toproject into the crucible and enveloped therein by a jacket.
 4. Theapparatus as claimed in claim 3, wherein the jacket has a graphite baseportion and a steel head portion.
 5. The apparatus as claimed in claim1, wherein the radiator comprises a helically slitted graphite tube. 6.The apparatus as claimed in claim 1 wherein a heating system is disposedwithin the interspace.
 7. The apparatus as claimed in claim 1 whereinthe cover, the crucible and the furnace are connected together by meansof a water-cooled flange.
 8. The apparatus as claimed in claim 1,wherein the crucible base portion is connected to a container permittingthe removal of slag under vacuum, and the crucible head portion isconnected to a valved reservoir permitting the supply of reactionmaterial to the crucible, under vacuum.
 9. The apparatus as claimed inclaim 8, wherein the container is fitted with a heatable conduitconnecting it to the crucible.